The present invention relates to a process for producing a plasma display panel (PDP).
According to the production process of the present invention, a pattern of a barrier for defining a discharge space, an electrode, a resistor, a dielectric layer or the like can be easily and uniformly formed by sandblasting. The plasma display panel according to the present invention is excellent in uniformity of in-plane brightness by virtue of a high-definition, uniform barrier structure. Further, since the barrier layer is colored, it is possible to improve the contrast and to improve the luminescence brightness of the phosphor.
PDP generally comprises: two opposed glass substrates; a pair of electrodes systematically arranged in the glass substrates; and a gas (mainly neon, xenon or the like) sealed therebetween. A voltage is applied across the electrodes to produce discharge within minute cells around the electrodes to emit light from each cell, thereby displaying information. In particular, systematically arranged cells are selectively subjected to discharge luminescence in order to display information.
Such PDPs are classified into two types, a direct current type (DC type) PDP, wherein electrodes are exposed to a discharge space, and an alternating current type (AC type) wherein electrodes are covered with an insulating layer. Each of these types is further classified into a refresh drive system and a memory drive system according to display functions and drive systems.
FIGS. 3 and 4 are a diagram showing a general construction of AC type PDP.
This AC type PDP is a plane discharge type PDP having a three electrode structure. FIG. 3 is a perspective view of the AC type PDP, and FIG. 4 a cross-sectional view of the AC type PDP in a plane parallel to a barrier. In these drawings, a glass substrate 12 as a front plate is shown separately from a glass substrate 11 as a back plate. As shown in the drawings, the glass substrates 12 and 11 are provided parallel and opposite to each other, and a barrier 8 stands on and is fixed to the front surface side of the glass substrate 11. This barrier 8 serves to hold the glass substrate 11 and the glass substrate 12 while leaving a given space between these substrates. Display electrodes X comprised of an electrode 14 of a transparent conductive layer and a bus electrode 15, which overlaps with the electrode 14, are provided in parallel to each other on the back surface side of the glass substrate 12, and a dielectric layer 16, covering the display electrodes X, and an MgO layer 17 are further provided.
On the other hand, on the front surface side of the glass substrate 11 are provided address electrodes Y orthogonal to the display electrodes X and a dielectric layer covering the address electrodes. Further, barriers 8 in a stripe form are provided parallel to each other or one another on the address electrodes Y, and a phosphor layer 19 having a predetermined luminescent color is provided so as to cover the wall surface of the barrier 8 and the bottom of the cell.
Each barrier is disposed between adjacent two electrodes Y so as to divide the discharge space in the line direction for each luminescent region.
In this AC type PDP, a predetermined voltage is applied, from an alternating current source, across the composite electrodes on the glass substrate 12 as the front plate to create an electric field, producing discharge within each cell as a display element defined by the glass substrate 12, the glass substrate 11 as the back plate, and the barrier 8. Ultraviolet light produced by the discharge permits the phosphor layer 19 to emit light, and light transmitted through the glass substrate 12 is viewed by an observer.
A conventional method for the formation of a barrier for PDP comprises conducting, once or a plurality of time, the step of printing a barrier-forming material on a substrate so as to correspond to the shape of a barrier pattern and drying the print to obtain a desired height.
Another conventional method for the formation of a barrier for PDP comprises the steps of: coating a barrier-forming material on the whole surface of a substrate; patterning a resist, possessing sandblasting resistance, in a predetermined form on the coating; performing sandblasting to remove areas not protected by the resist; and then separating and removing the resist (see Japanese Patent Publication No. 58438/1992).
Pattern formation by screen printing raises the following various problems. Firstly, stretching of a screen used in the printing is unavoidable, and, hence, misregistration between the screen and the electrode is likely to occur. Secondly, since a screen is used in the plate, distortion of the pattern is likely to occur, making it difficult to form a fine pattern. Thirdly, the barrier-forming material is travelled toward the backside of the screen plate, requiring wiping each time and the like. This makes it difficult to automate the pattern formation. Fourthly, the dimension of the finest pattern which can be formed by the screen printing is about 100 .mu.m in width, and the shape of the pattern is such that the ratio of the half-value width to the bottom width (half-value width/bottom width) is about 0.5. Therefore, a large bottom area is necessary for forming a pattern having a large height, posing a problem that no definite pattern can be formed.
The term "half-value width" used herein refers to the width of a stripe pattern or the like in the position of the half of the height of the stripe pattern (barrier) or the like.
In order to avoid the above problem, a method not relying on the screen printing is considered wherein a low-melting glass paste as a barrier-forming material is coated all over the surface of a glass substrate so as to uniformly cover the glass substrate to form a layer which is then partially cut out with the aid of sandblast. This method is called "sandblasting."
In this case, uniform coating of the glass paste followed by firing at such a temperature that the glass frit is completely fused, renders the cutting remarkably difficult. On the other hand, when firing is performed at such a temperature that the resin component is burned off and the fusing of the glass does not occur, the cutting rate is so high that control of the cutting is difficult. In this case, therefore, cutting of the coating in a paste state before firing is advantageous. In the case of cutting of a glass paste before firing, selection of the content and kind of the binder so as to provide a high cutting rate results in deteriorated adhesion between the cutting mask of a photosensitive resist material and the glass paste layer and, hence, creates separation of the cutting mask, making it impossible to form a barrier having a contemplated shape. On the other hand, selection of the content and kind of the binder so as to provide high adhesion results in separation of the glass paste material together with the cutting mask at the time of separation and removal of the cutting mask after the cutting due to good adhesion between the cutting mask and the glass paste layer, posing a problem that the shape of the top of the barrier is broken.
In the above method using a cutting mask, a dry film, for example, is used as the resist. In this case, a process involving the step of application of a dry film, the step of exposure, the step of development, the step of blasting, and the step of separation of the dry film is necessary. This process is long and troublesome.
The present invention has been made with a view to solving the above problems, and an object of the present invention is to provide a process for producing a plasma display panel which enables a high-definition, large plasma display panel having a pattern possessing a uniform shape to be produced in a simple and efficient manner.
Further, in the present invention, the use of different colors for respective layers constituting the barrier results in enhanced brightness and improved contrast of the display.